TAMING TECHNOLOGY FOR PRESERVATION

Americans have always been quick to seize upon theadvances of science to benefit their daily lives. ln 1750,Benjamin Franklin, in the same let ter in which he re-ported bis discoveries on electricity to the Royal Societyof London, described how a system of pointed iron rodsand grounding wires could be mounted on buildin~ toafford protection against lightning. Undoubtedly, thelightning rod is the earliest instance of American tech-nology applied to building preservation.More than two centuries later the preservation of build-ings, as weIl as historic districts, bas become the goalof numerous government programs and citizens groupsthroughout the nation. However, preservation is a com-plex task. Once preliminary considerations (i.e., publicrelations, legal, planning and financial arrangements) areresolved, preservationists must nex,t contend with thewhole range of physical problems that beset old build-ings. These may include deteriorated materials and fin-ishes, structural failures, obsolete installations, insensi-tive alterations and perhaps even a lack of skilled crafts-workers to execute the restoration work.To remedy these problems and reduce subsequent main-tenance, we look to our technological prowess for assis-tance. Unfortunately, our attempts to apply the techno-logical developments in other fields to the needs of his-toric preservation rarely have been so spontaneous orbeneficial as Franklin's example. A survey of the use ofmodern technology in the American preservation move-ment reveals a wide gulf between potential and practice.

PROBLEMS IN THE USE OF TECHNOLOGY

were consumed by this exercise of restoration zeal. Untilrecently, both the public and many professionals oftenfailed to realize that such features as authentic materialsand craftsmanship or subsequent modifications are morevaluable than a modern approximation of the original

appearance.Secondly, the architect and historian are handicapped intheir understanding of the proper.ties and behavior ofhistoric building materials, as weIl as in the effective useof modern technology. Without adequate background inscience, they find it difficult to communicate, let alonecoIlaborate, with research .technologists, who presumablycould bring their expertise to bear on preservationproblems.Finally, it should be recognized that contemporary tech-nology is limited in its application to building preserva-tion. Most of the technological advances of recentdecades have been produced by industrial researchlaboratories in response to a specific problem. The newproduct developed usuaIly meets the carefully definedneeds of the problem at hand. If a new advance findswider application, it is generally a fortuitous circum-stance, as in the case of the material Teflon, first devel-oped for rocket nose cones and now used to coat cookingutensils. Because no research laboratory in this countryis devoted exclusively to the needs of building preserva-tion, we are dependent on happenstance for techniquesand products from private industry that will benefit ourendeavors. Even when a technological innovation maybe of value to historic preservation, many problemsoften bar its ready use. For example, there are obvioustime lags that result from poor communications. Sincearchitects rarely read research abstracts and most indus-trial researchers are not concerned with old buildings,years may pass before the proper connection is madebetween those groups. A further problem is that onceadopted, an innovation may prove to be costly, toodifficult ,to be applied in the uncontroIled conditions of abuilding site, or simply incompatible with historic build-ing materials.The problems that may arise with technological inter-vention in historic .preservation are iIlustrated in the useand abuse of synthetic materials developed by the chemi-cal industry over the past several decades: coatings,adhesives and composites. The preservationist now hasan opportunity, for the first time, to use these and othernew materials in the conservation of our cultural heri-tage. These materials have frequently been seen as apanilcea that would arrest deterioration of historic build-ing elements, as weIl as a means of reducing buildingmaintenance. However, the improper application of these

For the most part, the preservation movement has beenslow to use the vast array of technological innovationsthat have had such profound effects on most Americanenterprises. The traditional nature of preservation work,the limitations of professionals in the field, and the fre-quent incompatibility of modern techniques with his-toric fabric have alI tended to pose impediments to theready use of technoloiïcal advances made in the physicalsciences. Further examination of these three impedimentsmay help to explain the current dilemma.ln the fust ins-tance, the aim of most preservationists inthis century bas been to recapture bistorical ambience,or at least create a modern approximation of historicreality. Very often, when materials have deteriorated orfeatures bave not canformed ta the desired image, tbeseelemelits bave been replaced with new building fabricto better facilitate "painting the picture," as restoratian-ists used ta say} Authentic elements of many structures

materials bas sometimes hastened the deterioration of theresource that they were intended to preserve.This misfortune bas been demonstrated by numerousattempts at adobe preservation in the Southwest. Adobe,or sun-dried ear,th brick, is the softest, most porous formof masonry; therefore, it is very susceptible to erosion by

weathering. Traditionally, adobe was maintained byperiodic replastering with a new coat of roud. To avoidthis maintenance, several synthetic treatments have beenused, with unfortunate results. For example, the applica-tion of clear waterproof coatings has tended to trapmoisture within the walls by reducing the natural per-

Since 1971 the Historic American Buildings Survey (HABS)has conducted photogrammetric projects in New Mexico andArizona to record Indian pueblos, early Spanish-Americanvillages and mission churches, prelhistoric cliff dwellings and theAnglo-American architecture of mining towns and ranches. Afull range of aerial and terrestrial photogrammetric techniques,as weIl as reverse perspective analyses of 19th-century photo-graphs, has been used to record whole settlements of adobestructures with sculptured walls and irregular openings such asthe pueblo of Taos, New Mexico, shown here. (Myra Borchers)

Depuis 1971, le Historical American Buildings Survey (HABS)dirige des projets photogrammétriques au Nouveau Mexique eten Arizona pour enregistrer les villages indiens, les premiersvillages hispano-américains et les églises missionnaires, les habi-tations troglodytes préhistoriques et l'architecture anglo-améri-caine des villes minières et des ranches. Une serie complète deteclH1iques aériennes et terrestres, ainsi qu l'analyse photogram-métique de vues renversées de photographies du XIXo siècle, aété utilisée pour enregistrer des ensembles complets de struc-tures d'hab~tats aux murs sculptés et aux ouvertures irrégulièrescomme le village indien de Taos, au Nouveau Mexique, preséntéici.

Q4.

~I

PRESERVATIONISTS AS CONSERVATORS

Clearly, we DOW Deed a generation of competent pro-fessionals who can deal with historic structures in thelight of contemporary technology .For example, museumconservators, who share the aims and principles of pres-ervationists, have developed considerable knowledge onthe composition, deterioration and treatment of historicmaterials. Because .these conservators are thoroughlyskilled in both art history and scientific technique, theyhave bridged the gap between preservation and tech-nology .Their activities have not been entirely confinedto small-scale artifacts, since their work occasionallyinvolves large architectural sculpture and paintings onthe walls and ceilings of great monuments.

meability ( breathing characteristics) of the porous ma-terial, causing surface spalling. Similarly, fiberglasscoatings, which can be made to dUJplicate the color andtexture of adobe, have been used to cover large sectionsof walls. When natural movements occur in the adobe,the fiberglass is stressed and cracks. This allows rain topenetrate behind the coating, where it cannot evaporateeasily, and great mischief ensues.If architects and archaeologists are to act as ".para-tech-nologists," the above experiences demonstrate that theymust adopt proper research techniques before prescribingrestoration treatments. Furthermore, these professionalsshould be prudent enough to refrain from using irreversi-ble treatments, since unsatisfactory results may occur ormore effective techniques may be developed in the future.

The church at Tumacâcori, Arizona, was drawn photogrammetrically to distinguish between some 20 partial restorations that havebeen cal'ried out on this adobe structure since it was declared a national monument in 1906. (Historic Ame;rican Buildings Survey,Ferry Borchers)

L'église de Tumacacori, Arizona, a été dessinée photogrammétiquement pour distinguer les quelques vingt restaurations partielles quiont été réalisées sur cette structure depuis qu'elle a été reconnue comme monument national en 1906.

Q~

Over the past several years archaeologists engaged in a jointresearch project of the National Park Service and the Univer-si1y of New Mexico at Chaco Canyon in northwestern NewMexico have experimented with remote sensing techniques asaids in data gathering. The mapping and identification of sur-face features of prehistoric roadways in Chaco Canyon havebeen accomplished through extensive use of aerial imagery. Dycareful laboratory examination of aerial photographs, groundfeatures, heretofore unknown, can be predicted and subsequentlylocated in the field, such as the remains of this prehistoric cause-way near Penasco. (Manual of Remole Sensing by permission.American Society of Photogrammetry)

Ces dernières années, les archéologues se sont sont engagés dansun projet en commun du Service des Parcs Nationaux et del'Université du Nouveau Mexique à Chaco Canyon, au NouveauMexique de l'Ouest, et ont expérimenté les techniques télésen-sorielles pour rassembler les données. La cartographie et l'identi-fication des particularités de surface des chaussées préhistoriquesà Chaco Canyon ont été accomplies par une vaste utilisation defigures aériennes. L'étude détaillés en laboratoire de ces photo-graphies aériennes permet de prédire et de localiser les particu-larités de paysage, inconnues jusqu'ici, telles les ruines de cettechaussée préhistorique près de Penasco.

Realizing the parallel nature of their concerns, preserva-tionists and conservators have recently established closercontact, which has resulted in a broad range of endeavorsinvolving mutual interests: conducting symposia to dis-cuss ,technical problems, establishing training workshopsto deal with conservation techniques, and undertakingtechnical information publications.The formation eight years ago of the Association forPreservation Technology (APT), a joint Canadian-American venture, gave architects and preservationistsan effective forum for exploring the application of scienceand technology to architectural preservation. Through itsquarterly Bulletin, the bimonthly Communique, annualmeetings and periodic technical courses, APT has beenof inestimable value in improving the quality of profes-sional practice in the field of building conservation.2

Several governmental and private organizations acrossthe nation are paralleling the endeavors of APT by plac-ing greater emphasis on preservation technology in theiroperations. ln the National Park Service, which fordecades has been the national leader in the developmentof preservation standards and techniques, the recentreorganization of the Office of Archeology and HistoricPreservation includes the creation of a Division of Tech-nical Preserva'tion Services. Drawing on years of prac-tical experience obtained by National Park Servicepersonnel, the new division will furnish technical adviceand consulting services to other agencies of the federalgovernment and to state and private preservation groups.

ln addition, the National Trust for Historic Preservationis presently expanding its technical assistance staff inWashington and its regional offices, in order to respondto the increasing demand for expertise on building con-servation problems throughout the nation. The Societyfor the Preservation of New England Antiquities(SPNEA) in 1973 formed a new department of tech-nical consulting services to accommodate a similar needin the New England region.ln 1970, New York State's Division for Historic Preser-vation organized a Bureau of Preservation and Restora-tion with regional restoration crews. This program, inaddition to accomplishing the restoration of state historicsites, provided opportunities for training craftsmen,developing new restoration procedures, and educatingthe public on preservation techniques through day-Iongseminars.Some of the most fruitful collaboration between con-servators and preservationists has occurred in the severalsymposia conducted in recent years. The most ambitiousof these ventures took place in September 1972, whenthe International Centre for Conservation sponsored aconference in both Williamsburg, Virginia, and Philadel-phia, Pennsylvania. The subject was "Preservation andConservation: Principles and Practices." For five days,t40 practitioners in the fields of conservation and preser-vation exchanged experiences and explored mutualproblems. The proceedings of this conference were pub-lished this year by the National Trust; the volumeconstitutes a compendium on architectural conservation.3

Another symposium. entitled "Building Early America,"

96

Since 1964 the Schoo1 of Architecture at Columbia Uni-versity in New York City has conducted a two-yeargraduate program in restoration and preservation ofhistoric buildings to train professional preservationists.Under the direction of Professor James Marston Fitch,the curriculum has stressed an interdisciplinary approachto preservation in which each year several dozen pro-fessional experts serve as guest lecturers. The courseexposes ~tudents to a wide range of specialists' knowl-edge, ranging from the techniques of archivai researchand architectural recording to knowledge of historicalmaterials and modern conservation techniques.

was organized by the Carpenters' Company of the Cityand County of Philadelphia in 1974 to commemoratethe 25Oth anniversary of the group's founding. Theagenda was divided in two parts: the fust dealt with thehistory of American building, with emphasis on materialsand construction techniques; the second was concernedwith contemporary preservation efforts. The proceedingsof this conference have aIso been published.4While the content of these two symposia was wide-ranging, other meetings have been conducted on selectedtopics to aIlow more in depth treatment. In March 1973,SPNEA and APT joint I y sponsored a conference on theperformance of old and new mortars in old masonrywalls.5 The Geological Society of America presented aseries of lectures on stone conservation during its 1974annual meeting. The annual meeting of the AmericanConcrete Institute in 1975 involved a one-day sympo-sium on the restoration of historic concrete structures.Training courses have aIso proven to be effective vehiclesfor dispensing newly developed technical know-how. InMayof 1975, the National Park Service and the NationalTrust sponsored a one-week course designed to provideadministrators of historic sites with a background onhistoric preservation maintenance.6 This year APT isconducting a course on the deterioration and preserva-tion of wood.7 A similar session on the use of polymeradhesives in the repair and restoration of buildings wassponsored 1ast year by APT at Colonial Williamsburg.These training sessions on the application of newlydeveloped specialized techniques have been carried onlargely by preservationists and conservators as continu-ing education programs for professionals.

X-ray examination of wood structures provides a nondestructivetechnique for da,ting building elements. Analysis (}f the varioustypes of nails-hand wrought, cut, and wire-revealed in X-rayphotographs together with data concerning probable construc-tion and renovation dates helps establish construction sequence.In a house built in 1763, X-ray photographs showed that turnedbalusters in an old &tair, fastened with wire nails, dated froman early 1900s renovation. Other portions (}f the stair balustradehad wrought nails that indicated a pre-1795 construction datefor some elements. Simi1ar interpretation of nails found in anX-ray photograph of a section of wall paneling in a h(}use builtin the 1790s, remodeled in the 1860s and again in the 1950s,showed t'hat wrough,t nails were used in the original con&truc-tion, cut nails in the 1860s and wire nails in the 1950s. (DavidHart, National Park Service Handbook for Historic Preserva-lion)

L'étude radiologique de StruotUTes boisees e&t une tecOOiqueinoffensive de dater les éléments de construction. L'analyse devariétés de clous -façonnés à la main, taillés, trefilés -révélés icidans les photos radiologiques de pair avec les données concernantles procédés problables de construction et de date de rénovation,aide à etablir la série des constructions. Dans une meison bâtieen 1763, les photographies radiologiques ont montré que lesbalustres tournées d'un viel escailier, fixées par des clous préfilés,dataient d'une rénovation du début du XIX. siècle. A d'autresendroits de la balustrade, des clous façonnés rndiquai~nt uneconstruction antérieure à 1795 pour certains des éléments. Uneinterprétation semblable de clous trouvés dans la photo d'unesection de panneau mural dans une maison construite dans lesannées 1790, remodelée dans les années 1860 puis en 1950,montrait que des clous façonnés avaient été employés dans lapremière construction, des clous taillés en 1860 et des cloustréfilés en 1950.

WIRE NAIl

WROUGHTNAIL

cur NAIL

Core-boring a 17th-century girl. ln order not to trap sawdust,the holIow bit is frequently made to slide in and out of thecore-hole while ill motion. (s.PNEA)

The tools necessary for field dendrochronology: A variable-speed drill, starting plate and sta.rting bit, coring bits, and awire to break Ioose the core once finished. The key to the feasi-bility of this technique lies in .the nonbinding bits, which aremade of a meta! alloy that expands little or not at ali under theextreme heat produced in the coring process. (Society for thePreservation of New England Antiquities)

Perforage d'une poutre du XVII" siècle. Pour éviter que lasciure ne pénètre à l'intérieur, on fait souvent glisser la mècheoreuse en mouvement de l'interieur à l'extérieur du trou deperforage.

Les outils nécessaires pour les ouvrages de dendrochronologie:une perforeuse à plu&ieurs vitesses, une plaque et une mèche demise en marche, des mèches de perforage et un fil pour détacherle noyau une fois le processus terminé. Le secret de la faisabilitéde cette technique repose dans les mèches non agglornérantesfaites d'un alliage de métaux qui se dilate peu ou pas du toutsous l'action de la chaleur extrême dégagée par le perforage.

The preservationist/conservator dialogue is further aug-mented by a growing body of technical publications. Forexample, the introduction earlier this year of a newmagazine, Technology and Conservation, indicates theconverging interests of these two groupS.8 This magazinewill concentrate on the application of science and tech-nology to building preservation and art conservation.ln addition to publication of the conference proceedingsalready mentioned, various government agencies havebeen issuing other technical publications and restorationreports. For instance, the National Park Service bascommenced a multivolume technical handbook on thestate-of-the-art in preservation.9 This project of the Officeof Archeology and Historic Preservation is assemblingpreservation expertise gained over the past severaldecades. The first volume of the series, Cyclical Mainte-nance for Historic Buildings, by I. Henry Chambers,was published earlier this year. To insure that the hand-book will reflect current developments and widespreadexperience, the Park Service is distributing preliminarydrafts of each section for comment and discussion byprofessionals in the field.l°

Since the demand for technical information is so press-ing, the Park Service is also preparing concise leafietscalled Preservation Briefs, on various handbook topics.These materials are for broad distribution to local groupsand individuals with limited technical preservation experi-ence. The first two leaflets in the series have dealt with

cleaningand repointing masonry.llTo supplement these publications and provide a vehiclefor an even wider ex change of ideas and experiences, thePark Service initiated in lune of 1976 a news bulletinentitled 11593. Also, the National Trust and ColumbiaUniversity have begun a series of publications on thetechnology of early American buildings, beginning witha volume on masonry construction.12 Finally, the Divi-sion for Historic Preservation in New York State haspublished reports on its research in 19th-century tinroofing and its experience in stabilizing an 18th-centuryornamental plaster ceiling.13Considered together, the foregoing recital of efforts mayappear impressive; however, all this is merely preliminaryte the actual work of preservation. To gauge properlyour accomplishments to date, we must take stock of the

projects executed. By reviewing the present record ofachievements in the various areas of building conserva-tion, we gain a better understanding of our weaknessesand strengths.

DOCUMENTING AND RECORDING

prepared for a restoration project. This procedure,which exploits the use of photographic emulsions appliedto mylar drafting sheets, does not require the sophisti-oated efforts of the methods described above. It savesconsiderable time in making field notations and prepar-ing contract documents; furthermore, the documents aremore readily comprehensible to both craftsworkers and

laypeople.1BEfforts in surveying and recording historic sites havebeen great I y augmented by the use of aerial and terres-trial photo-documentation. Archaeologists in the South-west concerned with surveying prehistoric Indian settle-ment sites are experimenting with various remote sensingtechniques developed by the military for photo-recon-naissance and by geologists for oil exploration. As aresult, airborne archaeologists now have at their disposaIseveral new da'ta-gathering systems.In addition to conventional aerj.al black and white pho-tography, these remote sensing techniques include infra-red scanning imagery, multispectral photography andradar. Application of these innovations has been limited;however, combined with tradition al ground-based tech-niques, they have the potential to greatly enlarge anarchaeologist's abilities to predict site locations, recordsites, and even assist in maintenance through periodicsurveying of conditions}9

NONDESTRUCTIVE INVESTIGATION

Before detailing the restoration of a building, an archi-tect must become familiar with its evolution and presentphysical condition. ln the past, m.any buildings weretom apart to obtain this information. This is no longernecessary; now we have begun to rely on some of thenondestructive testing instruments developed by manu-facturing industries to monitor the qua1ity of their goods.Some of these are laboratory instruments that can gen-erate data from very small samples of building materia1s.With other portable instruments, it is possible to performnonsampling analysis within the historic structure.

Museum conservators have used X-ray units extensivelyto investigate the internai structure of artifacts.2{1 In thepast few years, the National Park Service and SPNEAhave experimented with the use of portable X-ray equip-ment to determine the condition, configuration and con-struction history of hidden elements in wood structures.21Since a large portion of America's historic buildings areof wood construction (in which the structural membersare obscured under layers of paint, plaster and woodcladding) a nondestructive technique, as quickly andsimply performed as an X~ray examination, should findwide application.X-ray fluorescence and X-ray diffraction are two otherinvestigative techniques used by museum conservatorsbecause they require only small samples. While they holdpromise for the architectural conservator, these tech-niques have found only slight application in that field.ln X-ray fluorescence, the material to be analyzed issubjected to intense radiation, producing fluorescentenergy. Identifying the various wavelengths in this

The need to record and document our historic resourcesaccompanies nearly ail preservation activities. This pro-cess ranges from preparing archivaJ records for posterityto recording a building prior to restoration work, orsurveying an entire historic district for environmental

planning purposes.The Historic American Buildings Survey (HABS) of theNational Park Service is the federaI vehicle for thisextensive activity.14 Established in 1933 by the U.S.Congress, HABS is the Park Service's oldest existingpreservation program. Its summer field teams have pro-vided nearly two generations of architectural studentswith valuable experience in historic preservation. Boththe scope of its undertakings and a description of itsdisciplined techniques have been set forth in the HABSmanuaI, Recording Historic Buildings.15The Historic American Engineering Record (HAER)grew out of HABS involvement with engineering works.Founded in 1969, HAER is responsible for document-ing and recording our civil engineering heritage, includ-ing bridges, oanals, tunnels waterworks and industrialcomplexes.16Given the tremendous scope of the tasks confrontingHABS and HAER, they have used architectural photo-grammetry to provide an efficient, accurate and quickmethod of recording historic structures. The techniquesof photogrammetry and equipment used in this countrywere extensively developed in Europe. Once photo-graphic stereopairs of a subject have been taken andoriented within a plot ting instrument, orthographic viewsof the subject can be drawn directly by the instrumentoperator, who movesa measuring mark over the stereo-scopic optical model. Or the digital readout of the coor-dinates of innumerable points on the optical model canbe translated by a computer into graphic form. Thisrecording technique is weil suited to structures of com-plex, irregular form, or those with difficult access. Theplot ting instrument establishes a coordinate system formeasurement that would be difficult to establish on thesite. The use of photogrammetry in the United Stateshas been much less organized and intensive than in sev-eral European countries, but the technique has been

applied selectively during the past 20 years on a widevariety of projects. Most of these were sponsored bythe Historic American Buildings Survey and executedby Professor Perry Borchers of Ohio State University.Photogrammetry projects'have been undertaken to pro-vide drawings for restoration work, to record a structurebefore its imminent demolition, or to arouse PUblicawareness of the architectural quality of a buildingthreatened with destruction.17Another photo-documentation technique recently usedby architects consists of incorporating photographs ofexisting building conditions with the working drawings

Using the Obamber for Accelerated Decay (CAD), scientistsat the National Bureau of Standards, Gait!hersburg, Md., deter-mine &tone preserva:tive performance. ln the CAD, stone speci.mens are subjected ro dai I y test cycles under conditions tbat candegrade materials and their coatings, such as ultraviolet lig:ht,simulated air pollution, freeze-thaw, moisture and salt action.This Indtana gray lime&tone is shown (I) untreated; (2) treatedwith stone preservative before te&ting; (3) with preservativetrea1ment after 10 CAD test cycles, showing preservative treat.ment beginning ta flake; ( 4) after 20 CAD test cycles, showingincreased loss of stone preservative treatrnent. (National Bureauof Standards)

En utilisant la Chambre de détérioration accélérée, (Chamberfor Accelerated Decay)-(CAD), les savants du Bureau Nationaldes Normes, determinetrt la qualité des pierres préservatives.Dans cette chambre, les échantillons de pierre sont soumis àdes examens cycliques dans des conditions capables de detériorcrles matériaux et leur enduit, telles les rayons ultra-violets, lapollution stimulée de l'atmosphère, gel/dégel, humidité et activitésaline. Ce calcaire gris d'Indiana est présenté: ( 1) non-traité,(2) avant l'expérience, traité avec des pierres préservatives, (3 )après dix cycles dans la clIambre, le traitement commence às'émietter, (4) après vingt cycles, témoignant d'une perte crois-sante du 'traitement preservatif.

Recently developed synthetic materials, such as epoxies, o/fer ne-w possibilities to retain deteriorated himoric building materials ratherthan replacing them wi,th new materials. It is a common misconception that alI epoxy materials are rigid. A polysulfide-modified epoxyfiller, one of several developed by the Society for the Preservation of New England Antiquities, was used to attach these two piecesof wood, thus displaying IJhe fiexibility that can 00 attained with special formulations of these materials. (Norman Weiss)

Des matériaux récemment développés comme les époses offrent de nouvelles possibilités de maintenir 1e5 matériaux premiers desbâtiments historiques détériorés, plutôt que de les remplacer par de nouveaux matériaux; C'est une conception ordinairement erronéeque de coire à la rigidité de ces matériaux époxiques. Un mastic Çpoxique de polysulfide modifié-l'un des nombreux masticsdéveloppés par la Société pour la Conservation des Antiquités de la Nouvelle Angleterre, utilisé pour attacher ces deux blocs de bois,démontre la flexibilité quqe l'on peut obtenir par les différentes formules de ces matériaux.

fluorescence allows the diverse constituent chemical ele-ments in the material to be detected and measured. Byrecording distinctive patterns of diffracted X-rays thatvary according to the spacing and arrangement of theatoms in a crystal, X-ray diffraction aids in the identifi~cation of chemical compounds in a material. Theseanalyses can be extremely helpful in understanding thecomposition and behavior of historic building materials.22

A very different form of nondestructive analysis isdendrochronology, the study of the chronological se-quence of annual growth rings in trees. It is hoped thatthis technique will soon provide fairly accurate datingof wood structural members in buildings within a par-ticular climatic zone. The Laboratory of Tree-RingResearch at the University of Arizona in Tucson hasbeen the main center for this activity in the UnitedStates. In the past year, this laboratory's staff has assistedSPNEA in undertaking the necessary research to begintree ring dating of structures in New England.23It is becoming increasingly common for architecturaloffices specializing in preservation work to undertakesimple forms of material analysis, such as gravimetric(weight measurement) mortar analysis and microscopicanalysis of paint. No doubt this practice has largely corneabout as ,the result of specialists publishing their experi-ence with these analytical techniques in technical journalsand leaflets.24

PRESERVATION OF MATERIALS

the case of adobe, the problems that can develop whenthe surface of a porous material is made totally imper-meable to water.Such coatings as silicone that are merely water repellent,without eliminating vapor transmission, generally seemsafe, especially when the preliminary analysis of theoverall structure indicates few problems with condensa-tion and rising ground water. Nevertheless, so~e well-publicized failures (probably in instances where ,themasonry units themselves contain water soluble saltsprior to treatment) have made most preservationistswary of silicone coatings until more systematic field datacan be gathered.27The use of adhesives has been expanding slowly in .thepast few years with the encouragement of APT andother professional societies. Last year's APT trainingcourse on polymer materials paved the way for moreenthusiastic cooperation between preservationists and anumber of corporations currently making structuralrepairs with high-strength adhesives.28 Patching damagedmasonry has been greatly simplified by the use of newresins in the formulation of polymer-mineral compositesthat look like natural stone. However, a persistent prob-lem appears to be ,the tendency of some of these mate-rials to discolor upon prolonged exposure. This resulthas been attributed to the photochemical degradationof many of the new synthetics, especially epoxies. Anumber of laboratories trying to resolve this issue arealso looking at the use of epoxies, urethanes and organo-silicates for impregnation of stone, brick and plaster.~ Aclosely related investigation into the use of soil consoli-dants in the stabilization of archaeological sites hasrecently been carried out by the Franklin lnstitute inPhiladelphia as part of a larger program of preservation-related research.30The preservation of architectural wood and metal hasadvanced steadily as the result of a few important proj-ects. SPNEA recently completed a study of material forwood conservation that included the formulation of asemiflexible filler based on polysulfide-modified epoxyresins. Practical experimentation with this product is Dowunderway .31An interdisciplinary team of scientists and conservatorsat Washington University in St. Louis, Missouri, isresponsible for a number of major breakthroughs in thetreatment of outdoor bronze sculpture. The size of thesemonuments prompted the search for a rapid but safemethod of cleaning. After extensive comparative testing,glass bead peening proved to be the most suitableapproach. This technique, a modification of an olderindustrial procedure, bas found parallel use in the clean-ing of buildings in Venice.32 The application of corro-sion-inhibiting protective coatings has also been an inter-est of these researchers, who have already treated severalmonuments in St. Louis with dramatic results.33

The field of materrals preservation is probably the mostdifficult specialty of architectural conservation. Unlikethe processes of recording and investigation, mo&t of thetechniques used in treating materials involve seriousintervention-usually chemical-in the fabric of a his-toric building. The current concern to preserve materialsin situ has led preservationists to seek processes tha't willrestore finishes, arrest deterioration, strengthen materialsand in general reduce maintenance.These are worthy ambitions, but unfortunately manyattempts have produced irreversible damage. The bestresults have occurred when a particular problem is care-fully diagnosed, alternative procedures are tested, andlong-range effects are observed before treatment is at-tempted in the field. Hence, many of the mostpromisingtechniques for conserving building materials remain intheir infancy; these include impregnations, adhesiverepair and composite patching.25 Some of these tech-niques are still in an experimental phase, with limiteduse and little solid .accomplishment.The past two decades have seen the widespread use ofpolymer coatings for e~terior masonry. The applicationof such finishes is olten suggested in the belief that thesetreatments will prevent water intrusion and therebyeliminate weathering, staining and efflorescence. Recentstudies by the National Bureau of Standards' Center forBuilding Technology have confirmed the practical obser-vation of many building conservators that mostcommet-cially available coatings do not provide an easy answerto preservation problems.26 We have already noted, in

PHYSlCAL INTERVENTIONS

Technological intervention in a historic building is notlimited to chemical treatments. Every preservation proj-ect involves the conflict between the demands of modern

the combustion process, and leaves no residue or dam'ageto furnishings.35Finally, all forms of technology, both historic and con-temporary, are applied at the building site by craftswork-ers and specialists. The ultimate success of our interven-tions largely depends upon their skills. Realizing this, theNational Park Service established in 1956 its BuildingRestoration Specialists Program, which aimed to developcraftsmen's skills and build up a core of trained mechan-icsfor employment on Park Service restoration projects.The National Trust and several state preservation agen-cies have subsequently adopted similar programs.

COMPUTERS IN HISTORIC PRESERVATION

usage and the fragility of historic construction. Theinstallation of various intemal sy&tems, such as mechani-cal equipment, sanitary facilities, electrical installationsand fire detection/suppression systems often constituteserious threats to the historic integrity of a building. Theproblems presented by building, fire safety and seismiccodes are different, but frequently cause fundamentalalterations in an old structure.34Intemal systems usually have a life span th,at is but afraction of the total life of the buildings in which theyare installed. It is not uncommon to find old buildingsriddled by the various heating systems installed over theyears. Original fireplaces were superseded by stoves;,these in tum were followed by a variety of central heat-ing systems using pipes and ducts. We now realize thatheating and air-conditioning systems become obsolete in20 to 30 years; plumbing and illumination systems havea similar history .If old buildings are not to be mutilatedcontinually by these installations, we must develop small,compact systems that can be inserted in a structure witha minimum of cutting and patching. Industry bas yet toproduce a system that can fill this need. Perhaps theubiquitous window-mounted air-conditioner units, whichdo not require pipes and ducts, are a reasonable interimsolution.In historic buildings that contain valuable artifacts,another problem is encountered with environmental con-trol systems. Because buildings and artifacts requireddifferent optimum temperature and humidity levels, ad-ministrators of historic properties must often decidewhether ,the structure or its contents receives preference.A decision to favor contents can have disastrous effectson historic buildings in cold climates. When humidity israised to the level best for artifacts, condensation withinwalls of an uninsulated structure can result in wood decayand lime mortar decomposition.Since the technology of intrusion and fire detection/sup-pression systems is rapidly changing and developing,most installations today run the risk of rapid obso-lescense. Several effective intrusion systems, using ultra-sonic motion detection or pressure sensitive devices, arenow available. Their installation requires only minimalintervention in the historic fabric of a structure.

For example, an ionization detection system, which isextreroely sensitive to combustion in the incipient stage(before smoke and flammes are produced), can be in-serted inconspicuously in an existing building as anentirely surface-roounted installation. This systero con-tinuously draws samples of air froro each space in thebuilding through a series of small plastic tubes connectedto a central monitor; there the percentage of combustionparticles ( ions) is measured. When the percentage ex-ceeds a predetermined level, an alarro is sounded.

America is the land of the computer in the eyes of there~t of the world; yet, the historic pre~ervation movementhere bas barely begun to use the computer as an infor-mation manager. An examination of computers in his-toric preseNation therefore must deallargely with poten-tialities. By and large, preservationists have been intimi-dated by computers, which they view as costly and alienventures. Thus, the required investment in planning andprogramming bas not been forthcoming.As the need for coordination in the preservation fieldbecomes more urgent, computers will play a larger role.The most likely sources of computer activity are stateand federal agencies, which may in turn make computerservices available to local agencies. The directions forthe growth of the computer as an information managerfor historic preservation parallel those in other fields,such as the physical and social sciences. These directionsinclude: information storage and retrieval, business andcommunications management, computer-assisted publica-tions, and design graphics.Information storage and retrieval is one of the mosturgent needs in the management of such preservationrecords as site inventories and case studies. Computerretriev.al is useful in two important ways: in isolating aparticular record from a large collection, and in drawingsummary conclusions from the body of stored informa-tion. For example, a governmental agency might wantto reassess the impact of its grant programs on a num-ber of related buildings. Summary reporting from manualfiles is generally difficult and expensive because of thelabor involved in manually retrieving each record froma file cabinet. Computer~assisted retrieval significantlyminimizes clerical labor, renders the ope ration bothfaster and more economical, and eliminates much of thehuman error of manual work.The most critical need for automated information retriev-al in preservation is in the area of inventory manage-ment; central, authoritative historic property lists, whichcould serve as a basis for future planning, are lacking.The National Register of Historic Places is itself anattempt to compile a single, central list at the federallevel. Because of financial limitations and the lack of anationwide standard for recording, only a few state inven-tories have been automated. ln most cases these inven-tories have not used the recently developed class ofprogramming systems known as DBMS ( data base man-

ln the past, internai fire suppression systerns were largelylirnited to sprinklers; this often caused more darnage toa structure and its contents frorn water than from thefire. It js now possible to provide systems that deluge aspace with an jnert, liquified gas such as "Halon"( CF.'lBr ) .When triggered, this gas vaporizes into the firezone, extinguishes the fire by chemically interfering with

agement systems) , which allow the nontechnical usergreat flexibility in such areas as data design and retrieval.In the near future, the National Park Service's Registerof Historic Places, as weIl as the other surveys of theOffice of Archeology and Historic Preservation, areexpected to be installed on such a system.The wealth of accumulated experience in preservation isnot systematically collected, coordinated and made avail-able to those who could benefit from the knowledge. Thelack of sharing through a highly developed communica-tions network leads to the squandering of precious timeand resources. Although numerous organizations pub-lish information, hold meetings and otherwise dissemi-nate ideas, ,there is no single clearinghouse for alI phasesof preservation information. The United States lacks acomprehensive pooling of experience as to legal aspects,public policy and technical innovations. The scientific,legal and medical fields alI have developed clearing-bouses, often maintained under government auspices,which rely heavily upon computer support. In Canada,the Department of Indian and Northern Affairs bas de-veloped within its Restoration Services Division a com-puterized preservation data storage and retrieval system.This system, known as Infotech, demonstrates the effi-ciencies that computer technology can bring to the fieldof historic preservation.Design graphics bas been one of the most exciting appli-cations of the computer. For example, programs andequipment developed by aircI'aft and engineering corpo-rations and further refined at two universities have madeit possible to display perspective views of design alter-natives from continuously moving points of view. Also, asystem being developed by Professor Donald Greenbergand bis students at Cornell University displays scenes infull color, adding another design factor that can be pre-sented by computer. Using these systems, it is possibleto present streetscapes, individual building exteriors andeven interiors to those who might be reviewing a varietyof possible preservation alternatives in an old neighbor-hood. Applied to the aims of historic preservation, theimpact of losing a building in a community could thusbecome graphically clear. Alternate proposais could alsobe tested without the deceits inherent in architectural

renderings.The 'above uses of computers in preservation must alI bedeveloped, bu,t only in the sen se of applying existingtechnology to the field. Within the next five years, it isexpected that the sharing of facilities will reduce unitcosts and result in far wider acceptance of computers.Moreover, mutually exclusive, redundant, and noncon-forming independent systems should be avoided if thecomputer is to become an effective tool in managinghistoric resources.36

role for the benefit of historic preservation. To im:provethe competency of all professionals involved in the con-servation of our cultural resources, there must be nation-wide recognition of the problems confronting theirendeavors.The establishment in 1973 of the National ConservationAdvisory Council (NCAC) was an initial step in thisdirection. Comprised of a membership representing theleading institutions concerned with .the conservation ofour cultural resources, the Council has undertaken thestudy of conservation problems and the formulation ofrecommendations to meet the nation's needs in thisfield.37 Last spring ,the Council issued a preliminary re-port, Conservation of Cultural Property in the UnitedStates.38 That report urges creation of a national institutefor conservation, and several regional conservation cen-ters ,to deal more closely with various geographic areasof the nation. The national institute, as envisioned bythe Council, would serve the m,ajor areas of need: infor-mation ex change, education and training, and mainte-nance of a research mboratory .A central information ex change, functioning as a clear-inghouse, is badly needed for collecting and disseminat-ing experience gained in ,the laboratory on the one hand,and in field applications on the other. This ex changewould act as a liaison linking professionals, students andresearchers in private industry .In conjunction with an information ex change, a nationalpreservation education center could be active in con-ducting a wide range of continuing education coursesand seminars. Some programs could be directed to pro-fessionals, others might allow students and craftsmenon-the-job training, and still others could be designed toincrease public awareness of preservation issues.A national research laboratory, devoted exclusively topreservation problems, is a logical extension of theseinformation al and educational activities. At present,there are no government laboratories systematically con-cerned with the problems of deterioration in historicstructures.39 If extended tests and analysis of materialsand techniques were undertaken, this laboratory couldact as a catalyst in the proper use of technology in con-servation procedures. The laboratory could also estab-lish uniform standards for testing methods and for com-position of materials used in conservation.Another encouraging indication that the technical needsof historic building preservation are gaining wider recog-nition is seen in the proposaI of the Commit tee for theNational Museum of the Building ArtS.40 This groupadvocates the establishment of a national museum inWashington, one .that will focus public and profession alinterest on America's building heritage. At present, nota single museum in this country is devoted to the build-ing arts. Very often preservationists find themselves try-ing .to apply modern technology to building elementswhose origin, fabrication, or material characteristics theydo not fully understand. A collection of architecturalcomponents could form the basis of study of historic con-struction materials and techniques. Surely, creation ofsuch a museum, which has been proposed on severalprevious occasions,41 is vitally needed in view of thegrowing activity in historic preservation.

NEEDS AND GOALS

Since the time of Daedalus, the my th of the architect asa master of technology bas persisted. Despite Americans'inclination to equate "know-how" with technologicalexpertise, our architects are ill-equipped to exploit theadvances Qf technology and assume the conservator's

our national goals. The desire of the people to preservetheir architectural patrimony as an enduring part of theirdaily lives has been manifested in the Congress, statelegislatures and city councils. Conservation, restorationand recycling have now been accepted as ration al under-

takings.ln realizing these aims, we have throttled many of ourimpulses to waste and destroy. But beyond this achieve-ment, a further task remains. Our nation must now ano-cate the resources and train the personnel who win ulti-mately tame our technology to accomplish the purposesof historic preservation in America.

ln 1966, after extensively surveying conditions in thiscountry, the Special Commit tee on His,toric Preservation(formed by the U.S. Conference of Mayors) outlined itsrecommendations for a comprehensive national plan ofaction "to encourage, improve and reinforce public andprivate leadership" in the nation's historic preservationmovement. T,hese recommendations were set forth in thefinal chapter of the Committee's report, entitled WithHeritage Sa Rich.42Nearly alI of the Committee's recommend,3Itions havesince been acted upon, and preservatiol) laws have beenpromulgated. We have experienced a profound shift in

John I. MESICKCollaborators :

Perry E. BorchersWilfred Cole

Lee H. NelsonJohn C. PoppeliersNorman R. Weiss

RÉSUMÉ

Malgré l'inclination américaine à la technologie, la nationa toujours été lente à utiliser les innovations technolo-giques modernes dans le domaine de la conservationhistorique. Plusieurs facteurs ont empéché un plus vastesuccés de l'emploi de la technologie de conservation. Cen'est que depuis ces dernières années que de nombreuxconservateurs (preservationists) commencent à se pré-occuper de la conservation in situ des structures d'édificeshistoriques. La plupart des projets de restauration ont étéconfiés à des architectes et à des historiens qui, à causede leur formation et de leur expérience, ne sont familiersni avec les sciences ni avec la recherche technologiqueni avec la nature et le comportement des matériaux. Ledéveloppement de matériaux et de techniques conven-ables est retardé par le manque de facilités de recherchesconsacrées aux problèmes de la conservation d'édifices.Enfin, l'intervention de la technologie dans la restaurationde structures historiques présente souvent des problèmesd'incompabilité de matériaux qui peuvent causer ladétérioration involontaire de ressources historiques.Les conservateurs (preservationists) de bâtiments ontbeaucoup bénéficié de leurs contacts accrûs avec lesconservateurs de musées qui possédent une vaste expéri-ence de l'utilisation de techniques technologiques avan-cées pour la conservation d'objets façonnés. Une con-férence de cinq jours intitulée "Protection et Conserva-tion: Principes et Pratique," parrainée par le Centre dela Conservation à Philadelphie et à Williamsburg enSeptembre 1972, a fourni un forum incomparable auxconservateurs et aux "preservationists" pour examinerleurs problèmes mutuels. Une autre conférence, tenue

en 1974, "La Reconstruction de l'Amérique des PremiersTemps", organisée par la Compagnie des Charpentiersde Philadelphie, s'est occupée de l'histoire de la con-struction américaine, mettant l'accent sur les matériauxet procédés de construction et sur les nombreux effortscontemporains de conservation.Le souci croissant du progrès d'une technologie deconservation historique a conduit à la formation del' A ssociation A mérico-Canadienne " Pour l' A vancement

des Méthodes de Préservation (APT)" en 1968. Récem-ment, les opuscules disponibles sur l'histoire de latechnologie de construction et de techniques de conserva-tion d'édifices se sont multipliés, de manière significative,(voir les notes de renvoi) à mesure que plusieurs bureauxde conservation privés et gouvernementaux plaçaientdavantage l'accent sur les problèmes technologiques. LeService des Parcs Nationaux, qui depui.\" des décenniesest le chef de file national pour le développement denormes et de techniques de conservation, s'est embarquédans la préparation d'un manuel technique en plusieursvolumes qui s'occupe de l'état de l'art dans la conserva-tion. De plus, le Service des Parcs, le Trust Nationalpour la Conservation Historique et la Société pour laConservation des Antiquités de la Nouvelle Angleterreoffrent au public et aux groupes privés des conseils tech-niques et des consultations sur les problèmes de conser-vation.Les conservateurs américains (preservationists) ontobtenu un succès variable dans l'application des récentesinnovations technologiques aux divers aspects de laconservation d'édifices: documentation et enregistrement

des sites historiques, investigation sans dommages desstructures, traitement des matériaux historiques, installa-tion de systèmes internes dans les édifices et utilisationd'ordinateurs. La plupart de ces innovations ont étédéveloppées pour être employées dans d'autres domaineset actuellement commencent à servir de manière tentativedans le domaine de la conservation. Par exemple, lesarchéologues qui s'occupent de l'expertise des vestigesindiens du Sud-Ouest des Etats-Unis mettent en pratiqueles techniques télésensorielles développées par l' Armée ,telles que les figures de scrutation infra-rouges, la photo-graphie multi-spectrale et le radar: L'application de cestechniques télésensorielles s'est avérée limitée; cependant,une fois combinées aux techniques archéologiques debase, elles ofjrent la possibilité d'élargir grandementl'abilité d'un archéologue de prédire et d'enregistrer unsite historique. Dans d'autres domaines, le fossé entre

les possibilités technologiques et leur application pratiquedemeure grand. Le défaut de ne pas employer lesordina-teurs de manières variées est un exemple flagrant desdifficultés auxquelles se confrontent les conservateursaméricains dans l'exploitation des abondants moyenstechnologiques à l'avantage de leurs entreprises.Peu à peu, à mesure qu'une plus juste appréciation desproblèmes et des possibilités de remploi de la technolo-gie pour la protection des constructions gagne davantaged'élan de par la nation, des fonds sont alloués pour laréalisation des projets de conservation historique. Desprogrès se sont accomplis en vue de r éstablissementd'organisations qui faciliteraient la formation de con-servateurs d'édifices ( preservationists ) , le développementde laboratoires de recherche et la dissémination derenseignements techniques.

lines for Rehabilitating and Preserving Old Buildings, Neighbor-hoods, and Commercial Areas."Il. Robert C. Mack, AIA, "The Cleaning and WaterproofCoating of Masonry Buildings," Preservation Briefs I, 1975;Mack, '.Repointing Mortar Joints in Historic Brick Buildings,"Preservation Briefs 2, 1976. Available from ilie Office of Arche-ology and Hi~toric Preservaûon, National Park Service, U. S.Department of the Interior, Washington, D.C. 20240.12. Harley J. McKee, FAIA, Introduction to Early AmericanMasonry: Stone, Brick, Mortar and Plaster (WashingtDn:National Trust for Historic Preservation, 1973) .13. Diana S. Wai'te, Nineteenth Century Tin Roofing and IlsUse at Hyde Hall (Albany: New York State Historic Trust,1972); John G. Waite, The Stabilization of an Eighteenth Cen-tury Plaster Ceiling at Philipse Manor (Albany: New York StateHistoric Trust, 1972).14. For a more complete account of HABS activity, seeDocumenting a Legacy: 40 Years of the Historic AmericanBuildings Survey, reprint from t.he Quarterly lournal of theLibrary of Congress, October 1973.15. Harley J. McKee, FAIA, Recording Historic Buildings(Washington: National Park Service, U.S. Department of theIDterior, 1970). Order from Superintendent of Documents, U.S.Government Printing Office, Washington, D.C. 20402. Publica-tion No. 1.29.2H62/12. $6.50.16. HAER summer projects du ring 1974 and 1975 were des-cribed in Society for Industrial Archeology Newsletter, Supple-mentary Issues: No.7, December 1974, and No.8, April 1976,ediltor, Robert M. Vogel, National Museum of History andTechnology, Smithsonian Institution, Washington, D.C. 20560.17. These remarks on architectural photogrammetry have beenabstracted from a statement prepared for this article by Perry E.Borchers of Ohio State University, who introduced architepturalphotogrammeotry to this country. Also see Borchers, "Archi-tecturaI Photogrammetry in Restoration," Building Research,Vol. I, No.5, September-October 1964, pp. 18-19; and "Archi-tectural Photogrammetry for HistDric Preservation" (workingtitle), to be published by the Office of Archeology and HistoricPreservation, National Park Service, U.S. Department of the1nterior.18. Cynthia J. Phifer, "Using Photographs in Contract Docu-men{son Restoration Work," AIA Journal, February 1976, pp.44-47. Also, Richard Bergmann, in a paper read to the 1975annual meeting of APT, described his use of this technique inthe preparation of bidding documents for restoration of theWinder Building in Washington, D.C.19. For a more complete description of remote sensing inarchaeology, see George J. Gumerman and Thomas R.L'ions, "Archeological Methodology and Remote Sensing,"science, Vol. 172, 1971, pp. 126-132; Thomas R. Lyons, BasilG. Pouls and Robert K. Hîtchcock, "The Kin Beneola Irrigation

11'1"

Study: An Experiment in the Use of Aerial Remote SensingTechniques in Archeology," Proceedings of the Third AnnualConference on Remote Sensing in Arid Lands (Tucson: Uni-yersity of Arizona, 1972); H. Homer Aschmann, et. al., "People:Pas! and Present:' Manual of Remote Sensing Vol. Il (FallsChurch, Virginia: American Society of Photogrammetry, 1975),Chapter 26, pp. 1999-2060.20. An early use of X-rays !o examine artifacts was describedin Stewart Culin, "An Archaeological Application of the RontgenRay," Bulletin of the Free Museum of Science and Art, Vol. I,No.4, 1897, Philadelphia.21. See David M. Hart, "X-Ray Investigations of Buildings,"Bulletin of the Association for Preservation Technology, Vol. V,No.1, 1973, pp. 9-21; Hart, "X-Ray Analysis of the NarbonneHouse," Ibid., Vol. VI, No.1, 1974, pp 78-98; Hart, .'X-RayNon-Destructive Examination of Historic Structures," December ,1975, draft prepared for the National Park Service TechnicalBandbook for Bistoric Preservation.22. For a more complete treatment of these and other scientifictechniques used in archaeology, see Bernard Keiscll, Secrets ofthe Past: Nuclear Energy Applications in Art and Archeology(Oak Ridge, Tennessee: U.S. Atomic Energy Commission,1972); Scientific Methods in Medieval Archaeology, ed. RainerBerger (Berkeley: University of California Press, 1970).23. For a geneml description of dendrochronology, see C. W.Ferguson, "Concepts and Techniques of Dendrochronology,"Scientific Methods in Medieval Archaeology, pp. 183-200; MarvinA. Stokes and Temh L. Smiley, An Introduction to Tree RingDating (Chicago: The University of Chicago Press, 1968).24. A procedure for morta.r analysis was described in : E.Blaine Cliver, "Tests for the Analysis of Mortar Samples,"Bulletin of the Association for Preservation Technology, Vol.VI, No.1, 1974, pp. 68-73. PaiQt color analysis techniques havebeen described by Penelope Hartshorne Batcheler in Paint ColorResearch and Restoration, Tecllnical Leaflet 15 (NashviIJe,Tennessee: American Association for State and Local History,1968); Morgan W. Philips, "Discoloration of Old House Paints:Restomtion of Paint Colors at the Harrison Gray Otis House,Boston," Bulletin of the Association for Preservation Technology,Vol. III, No.4, 1971, pp. 40-47; and Morgan W. Phillips andNorman R. Weiss, "Some Notes on Paint Research and Repro-duction," Bulletin of the Association for Preservation Tech-nology, Vol. VII, No.4, 1975, pp. 14-16.25. The work of the Forest Products Laboratory at Madison,Wisconsin, founded in 1910 as a research unit of the ForestService, U.S. Department of Agriculture (USDA), provides anotable exception !o this statement. W'hile no! directly concernedwith the probiems of historic preservation, this laboratory basconducted extensive reseai'ch on the characteristics, use andpreservation of wood.The Forest Service has issued many publications reporting re-search by the laboratory. Recent titles of interest to buildingpreservationists include: Wood Bandbook: Wood as an Engi-neering Material, Agriculture Handbook No.72, revised 1974;Condensation Problems in Your Bouse: Prevention and Solution,Agricultuml Information Bulletin No.373, 1974; Principle forProtecting Wood Buildings !rom Decay, USDA Forest ServiceRes. Pap. FPL 190, 1973.Also, a trade associ~tion, the American Wood Preservers In-stnute, 1651 Old Meadow Road, McLean, Virginia, 22101,issues a bimonthly magazine and numerous technical publica-tions dealing with wood preservation.26. 'I1he CMter for Building Technology currently has inprogress a study of stone preservatives commissioned by theNational Park Service. See Gerald A. Sleater, A Review of theSubiect of Natural Stone Preservation (Washington: NationalBureau of Standards, 1973), available from National TechnicalInformation Service; Springfield, Virginia 22151.27. Mack, "The Cleaning and Waterproof Coating of MasonryBuilding," Preservation Briefs I, (Washington: National ParkService, U.S. Department of the Interior, 1975) p. 4.28. The Adhesive Engineering Company, San Carlos, Cali-fornia, is àmong the companies pioneering in the use of per-manent structural adhesives in pressure gro1Jting cracks in dams,highways and other large concrete struCtures.

29. Among the better known American investigators who havecarried out important research in this very specialized field are:K. Lai Gauri, Department of Geology, University of Louisville,Louisville, Kentucky; Seymour z. Lewin, Professor of Chemistry,New York University, 4 Washington Place, New York, NewYork 10003; Edward V. Sayre, ConservaMon Center of theIn~titute of Fine Arts, New York University, I East 78th Street,New York, New York 10021; Norman R. Weiss, Science Con-sultant, Haverhill, Massachusetts 01830.30. This project involved .the conservation of basement remainsat the site of the Benjamin Franklin house in Philadelphia. Thesite was excavated by the National Park Service and is part ofFranklin Court in Independence National Historical Park.31. This project was suppol'ted by the National Park Service.A report on the project will be published as one of the Hand-book series by the Office of Archeology and Historic Preserva-tion, National Park SeI'VÏce, U.S. Department of the Interior,Washington, D.C. 20240.32. Phoebe Dent Weil, "The Use of Glass Bead Peening toClean Large Scale Outdoor Bronze Sculpture," AJC Bu/1etin,Vol. 15, No. I, pp. 51-58, 1974; Weil, "Problems of Preservationof Outdoor Bronze Sculpture: Examination and Treatment ofThe Meeting of the Waters, in St. Louis, Missouri," AJC Bul-letin 1974, Vol. 14, No.2, pp. 84.92.33. This review of materials preservation, as outlined in thelast five paragraphs, was prepared by Norman R. Weiss forinclusion in this article. Mr. Weiss is a consulting scientistspecializing in conservation problems.34. The problems presented by building codes in preservingolder biuldings was the subject of a conference sponsored by theNational Trust for Histol'ic Preserva,tion in Washington in May1974. See Preservation and Building Codes (Washington: TheNational Trust for Historic Preservation, 1975) .35. The foregoing remarks on various internai systems havebeen prepared in collaboration with my associa,te in the Preser-vation/Design Group, John G. Waite, and in large measure re-fiect his experience in supervising the restoration of Olana (the1870 home of Frederic Church near Hudson, New York) forthe New York State Division for Historic Preservation.36. These remarks on computers in historic preservation havebeen abstracted from a statement prepared for this article byWilford Cole of the Office of Archeology and Historic Preserva-tion, National Park Service, Washington.37. The needs of architectural conservation were consideredby a special study commit tee chaired by Elliott Carroll, Execu-tive Assistant to the Architect of the Capitol. This committeeincluded in its membership representatives from organizationsconcerned with building preservation: The Nar,ional Park Serv-ice, The American In&titute of Architects, the National Trustfor Historic Preservation, the Advisory Council for HistoricPreserva.tion and the Association for Preservation Technology.38. Conservation of Cultural Properly in the United States(Washington: National Conservation Advisory Council, 1976).Copies of this report are available from Gretchen Gayle, Execu-tive Secretary, NCAC, c/o SI-356, Smithsonian Institution,Washington, D.C. 20560.39. As noted above, the Centerfor Building Technology in theNational Bureau of Standards has occasionally been commis-sioned by the National Park Service to undertake research proj-ects.40. Inquiries concerning this endeavor may be directed toCynthia R. Field, President, Committee for the National Museumof the Building AI'ts, 1800 M Street, N.W., Suite 400 S, Wash-ington, D.C. 20036.41. Charles E. Peterson, over the past four decades, has madeseveral proposais for a national architectural museum. See "AMuseum of American Architecture," The Octagon (Washing-ton: The American Institute of Architects, November, 1936),.'The Museum of American Architecture: A Progress Report,"Journal of the Society of Architectural Historians, Vol. I, No.3-4 (July-October 1941), and "The Role of the Architect in His-torical Restoration," Preservation and Conservation: Principlesand Practices, p. 6.42. With Heritage So Rich, ed. Albert Rains and Laurance G.Henderson, (New York: Random House, 1966).